class Student1(object):

    def __init__(self):
        print 123
    @property
    def birth(self):
        return self.__birth

    @birth.setter
    def birth(self, value):
        self.__birth = value

    @property
    def age(self):
        return 2014 - self.__birth

zz=Student1();
zz.birth=10

print callable(zz)

def foo(s):
    n = int(s)
    assert n != 0, 'n is zero!'
    return 10 / n
